Since the determination of human immunodeficiency virus type 1 (HIV-1) as the etiological agent of the acquired immunodeficiency syndrome (AIDS), several other retroviruses have been identified which share many structural, biological, genetic and antigenic properties with HIV-1. However, there are also significant differences in pathogenicity among these retroviruses. Of course, in order to understand various similarities and differences, the mode of transmission and the pathogenicity of these retorviruses, it is essential that specific reagents which rapidly identify and differentiate between various isolates of these retroviruses be readily available. Conventional molecular genetic methods currently employed for this purpose are expensive and time consuming, and the available commercial tests for HIV-1 recognize less than 50% of HIV-2 and SIV sera and vice versa.